Process flowsheet development for selective arsenic removal, lead and antimony recovery from lead softening slag

Abstract

ABSTRACT A pyro-hydrometallurgical process is proposed in this study for the selective arsenic removal and the Pb and Sb recovery from lead softening slag, which incorporates NaOH roasting followed by water leaching, carbothermic reduction, and HNO3 leaching as process steps. Lead softening slag, containing 63.9 wt% Pb, 17.7 wt% Sb, and 4.4 wt% As, is first roasted with NaOH at 400°C, followed by water leaching at room temperature. The effect of the roasting temperature and NaOH dosage is investigated with regard to the removal yield of As, Pb, and Sb. The arsenic-free slag is reduced with carbon for Pb recovery as the antimonial lead. The reduction temperature and carbon dosage are optimized by applying FactSage modeling and performing experimental tests for selective Pb recovery. The residual slag is leached with HNO3 solution for the further removal of Pb and enrichment of Sb. The chemical and phase composition of the final leaching residue is determined to assess the possibility of using it as a feedstock for antimony trioxide production. The proposed process flowsheet enables the recovery of Pb and Sb as antimonial lead and antimony trioxide, respectively.